147

MIL-STD-1553

The 1553 standard defines a time division multiplexed data

bus for application within aircraft. The bus is defined to be

bipolar, and encoded in a Manchester II format, so no DC

component appears on the bus. This allows transformer

coupling and excellent isolation among systems and their

environment.

The HD-15530 supports the full bipolar configuration,

assuming a bus driver configuration similar to that in Figure

1. Bipolar inputs from the bus, like Figure 2, are also accom-

modated.

The signaling format in MlL-STD-1553 is specified on the

assumption that the network of 32 or fewer terminals are

controlled by a central control unit by means of Command

Words. Terminals respond with Status Words. Each word is

preceded by a synchronizing pulse, and followed by parity

bit, occupying a total of 20

µs. The word formats are shown in

Figure 4. The special abbreviations are as follows:

P

Parity, which is defined to be odd, taken across all 17

bits.

R/T

Receive on logical zero, transmit on ONE.

ME

Message Error if logical 1.

TF

Terminal Flat, if set, calls for controller to request

self-test data.

The paragraphs above are intended only to suggest the

content of MlL-STD-1553, and do not completely describe its

bus requirements, timing or protocols.

FIGURE 6. SIMPLIFIED MIL-STD-1553 DRIVER

FIGURE 7. SIMPLIFIED MIL-STD-1553 RECEIVER

FIGURE 8. MIL-STD-1553 CHARACTER FORMATS

FIGURE 9. MIL-STD-1553 WORD FORMATS

NOTE: This page is a summary of MIL-STD-1553 and is not intended to describe the operation of the HD-15530.

“1”

“0”

BUS

“0”

“1”

BUS

+

-

+

-

“1” REF

“0” REF

COMMAND

SYNC

SYNC

DATA

PERIOD

BIT

PERIOD

BIT

PERIOD

BIT

LOGICAL ONE DATA

LOGICAL ZERO DATA

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

55

5

1

P

DATA WORD

COUNT

SUB ADDRESS

/MODE

TERMINAL

ADDRESS

SYNC

COMMAND WORD (FROM CONTROLLER TO TERMINAL)

1

R/T

16

1

P

SYNC

DATA WORD (SENT EITHER DIRECTION)

59

1

P

CODE FOR FAILURE MODES

TERMINAL

ADDRESS

SYNC

STATUS WORD (FROM TERMINAL TO CONTROLLER)

1

ME

TF

1

CONTROL WORD

HD-15530